This invention relates to a pivot assembly incorporating a detent that is used to connect a mirror head and mirror mounting bracket of a rear vision mirror. In particular, it relates to a pivot assembly having attachment means which enables it to be secured between a mirror head and mirror mounting bracket.
Vehicle mirrors, in particular, external side rear view mirrors, normally comprise a mirror head which is pivotally attached to a mounting bracket. The mounting bracket is in turn secured to the motor vehicle body. The pivot enables the mirror head to rotate with respect to the bracket to either allow movement of the mirror head if it is impacted either while the vehicle is moving or stationery (referred to as xe2x80x9cmirror break awayxe2x80x9d) or to move to a parked position under the action of drive means incorporate the mirror head to ensure that the mirror head is moved to position where it is as close to the vehicle body as possible.
A detent is normally used in the pivot. This provides a positive location and holding force for the mirror in various positions as it is rotated about the pivot. The detents resist initial movement of the pivot and require a minimum force in order to overcome the detent force.
Such detents are common practice in the field, and normally comprise either circular balls held between a surface of the mirror head and mounting bracket which locate within recesses or abutting ramped surfaces. The holding force is provided by a spring which is normally a coil spring located around a vertical spigot. The spigot is normally incorporated into the mounting bracket and the mirror head has an aperture which locates over the spigot. One disadvantage of this is the fact that the spigot on the bracket and the aperture within the mirror head tend to position the mirror further outward than might be desirable. This imposes certain limitations of the design of the mirror head which impact on its stability and ability to resist vertical loads. It also means the use of more robust materials such as die-cast components which are more expensive, and increases the amount of material required to manufacture the mirror.
The aim of the invention is to design a new style of pivot connection between a mirror head and mirror mounting bracket and to also address the problems referred to above.
In its broadest form, the invention is a pivot assembly connecting the mirror head and mirror mounting bracket of a rear vision mirror comprising:
a spigot;
a plate;
an aperture in said plate journalled to said spigot;
a detent between said plate and spigot that changes from a locked position, where said plate is held with respect to said spigot, to a disengaged position by rotation of said plate with respect to said spigot;
a spring acting against said detent to hold it in said locked position, said spring yielding to allow said detent to move to a disengaged position as said plate is rotated with respect to said spigot; and
attachment means on both said spigot and plate that allow said spigot to be secured to either one of said mirror head or said mirror mounting bracket and said plate to be secured to either one of said mirror head or said mirror mounting bracket to enable said mirror head to be held, or rotated with respect to said mirror mounting bracket.
One main advantage of the pivot assembly is its modular nature which enables a standard design of pivot assembly to be utilized between any mirror head and mounting bracket. All that is required is to standardize the area of the mirror head and mounting bracket between which the pivot assembly is located.
The invention also enables the pivot assembly to have a relatively small height by comparison to existing spigots. This in turn allows the glass of the mirror head to be placed further inboard and over the mirror mounting bracket which is not possible with existing spigot designs. This in turn reduces the moment arm of the mirror arm and decreases the amount of material required for manufacture of the mirror head.
There may be several means of attaching the pivot assembly to the rear vision mirror. In one instance, the pivot assembly may have a first and second plate which are spaced and parallel with one plate located above the other and attached to the mirror head, the lower plate being attached to the mirror mounting bracket. Alternatively, the invention may comprise a spigot and plate where the spigot is attachable either to the mirror head or the mounting bracket. For example, in the case of a mirror head that may be supported by one or more arms to the mounting bracket, the pivot assembly can be located within the arm with a vertical pin or bolt securing the spigot with respect to the mounting bracket.
A number of attachment means may be used to secure the pivot assembly between the mirror head and mounting bracket. These may include threaded fasteners which locate through plate elements and engage corresponding surfaces within the mirror head or mounting bracket or they may include pins or bolts which locate through the center of the spigot to thereby secure the spigot with respect to either of the components.
In addition, the attachment means may comprise elements which enable quick and easy attachment of the pivot assembly to the various components. For example, tabs or other projections which can locate into the apertures and be slid into position so that the tabs hold the pivot assembly with respect to the mirror head or mounting bracket. Non-return catches can be used to hold the pivot assembly in place and to prevent disengagement of the tabs from their apertures.
A variety of detents can be used. These may incorporated indentations and projections formed within first and second plates, or may also comprise detent elements which are held in recesses or notches between the rotating components. In both cases, the detents are held in their engaged or locked positions by a spring which can yield sufficiently to enable disengagement of the detents.
Preferably, the spring comprises a concave disc which may also have a negative spring rate as it yields during disengagement of the detent. A concave disc have a positive spring rate which changes to a negative spring rate as it is flexed towards a flattened position. This is an inherent property of such a design, and the degree of pre-tension load can be varied by changing material, material thickness, the degree of concavity, and the number of concave spring plates which are stacked together.
The use of a spring having a negative spring rate is that maximum force is applied to the detent at its pre-loaded position and that upon force being applied to the spring, the load applied to the detent reduces so that the force or torque required to rotate the mirror head also reduces. This provides maximum holding force while at the same time reducing the force required to rotate the mirror head once this holding force has been overcome.
An advantage of the use of the spring in the form of a concave disc is the significant reduction in height requirement by comparison to conventional coil springs. This in turn means that the pivot requires less vertical space thereby enabling the mirror to be positioned more inboard and over the mirror mounting bracket than otherwise possible. Accordingly, the concave disc spring will also have application in existing mirror pivot designs.
Various components of the pivot assembly are preferably produced from stamped metal components. However, other manufacturing processes such as casting, sintering or machining may also be used.
Further, the invention may also comprise a drive means which can be used to rotate the mirror head to the parked position. In this case, the detent acts as an override clutch which enables the mirror head to rotate should the mirror be subject to a break-away force or become jammed while being rotated to a parked position. This will prevent gears used in the drive means from stripping when break away or jamming of the mirror head occurs.